It is well known that, when tubular plastic film is extruded in a molten state from an annular die and then proceeds as an air filled bubble before being flattened by passing through a collapsing frame and between a pair of nip rollers, irregularities occur in the thickness (i.e. gauge) of the film. Since the film is usually then wound onto a storage roll, it is necessary to provide apparatus for moving the two layers of the flattened film relatively to one another so than an irregularity in film thickness, i.e. in its gauge, is distributed across the width of the storage roll to avoid the problems which would arise if this was not done. This process is commonly known as gauge distribution, and various types of apparatus have previously been used for this purpose. One type of gauge distribution apparatus is described in U.S. Pat. No. 4,676,728 issued Jun. 30, 1987, to Mirek Planeta, the contents of which are hereby incorporated herein by reference.
As typically shown in this prior patent, gauge distribution is effected by passing the flattened tubular film around turning bars whose angular orientation with respect to the film is varied. In such prior art, such variation of angular orientation has, for one reason or another, not been centred about the longitudinal axis of the extruded tubular film bubble, and this causes problems for which compensation must be provided.